An in-flight activity practiced by some ill-mannered travelers is about to become even more of a hot-button issue.

We’re not talking about reckless reclining, armrest hogging or even coast-to-coast wind-breaking. The topic du jour is surfing pornography, violent material or other inappropriate content on screens easily seen by nearby seatmates.

It’s icky, irritating, rude — and relatively rare — at least for now. But as Internet surfing becomes an in-flight reality, some flight attendants, passengers and parents are worried that the problem will grow.

I’d like to say I doubt it. Or that it’s a “non-problem,” as some spokespeople for airlines and technology companies have assured me. But, given that in the past six months alone I’ve had to ask one seatmate to turn off a gruesomely violent video and remind another to shield the close-up heart surgery video he was studying, I think we’re in for trouble.

Flight attendants as porn police?
Last July, when US Airways announced that it would begin charging passengers for coffee, tea and soft drinks, flight attendants objected on the grounds that they’re certified safety professionals, “not cashiers to be used” to bolster the airline’s bottom line.

Now that American Airlines is testing unfiltered Internet on some flights, flight attendants are worried that the role of “porn police” is being added to their job description.

Frank Bastien, spokesperson for the Association of Professional Flight Attendants, the union representing 19,000 American Airlines flight crew members, put it this way: “With all the pressures already involved with flying, why invite something else on board without fully considering the problems it may cause.”

Will airlines zip it up?
Airlines are still ironing out issues associated with paid, in-flight wireless service. Filtering is definitely on the list.

American Airlines spokesperson Tim Wagner told me the carrier's policy was to provide Wi-Fi capabilities “with unfiltered connections that allow customers to get what they need, when they need it.” A few hours later he sent an update: “[W]e want to be responsive to the feedback of our customers and employees. We are researching potential technology options that would filter pornographic content ...”

Over at Alaska Airlines, which will be soon begin testing and installing in-flight wireless service, spokesperson Marianne Lindsey says the current plan is not to limit content “as we are hoping that the close social environment of the aircraft cabin will encourage people to use good judgment in their Internet browsing.”

Virgin America, which plans to launch in-flight Wi-Fi in November, is hoping savvy flight attendants and socially responsible travelers will make filtering unnecessary. “Flight crews are trained to deal with the issue ... and they do everything they can to move passengers if (for any reason) they are uncomfortable ... due to a fellow passengers’ actions,” spokesperson Abby Lunardini said. However, she added, “We don’t believe that Wi-Fi accessibility will significantly change the formula as there is nothing stopping guests now from downloading the content onto a laptop. Most guests view being on a flight akin to being in any other public place and moderate their behavior accordingly.”

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What do travelers think?
Larry Traverso, a textile importer and distributor, says while he’d have no qualms about “politely saying something to the person next to me if they were viewing porn,” he believes it would be reasonable for airlines to block access. “I don't think we can trust the general public to police themselves and I don't think it is appropriate in a public place.”
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Peter Taylor, the father of two young kids, says unfiltered service raises red flags. For now, he’s confident he can keep his kids from seeing objectionable material on other passengers’ laptops, but as his kids get older he knows shielding them from inappropriate images will be harder. “My kids may have to sit in their own row or they might even fly on their own. And then I can’t do anything.”

Yet there are some, including author and motivational speaker Mellanie True Hills, who feel filtering won’t make a difference. “I've lost count how many times I've seen things that I consider objectionable on DVD players or computers while flying, so filtering Internet content on flights won't solve that problem. ... The problem is that we all have different standards of what is offensive.”

Different strokes for different folks
Different standards are definitely part of the issue, says Forrester Research’s aviation analyst Henry Harteveldt. He’s had his own first-hand experience dealing with a porn-watching seatmate. “I said ‘you don’t have a filter on your screen or blinders — I don’t care what you do by yourself, but please don’t watch it on an airplane.’ The guy was a little grumpy about it but he turned it off.”

Harteveldt, who emphasizes that he’s not a lawyer, says when it comes to paid in-flight Web surfing, he suspects some people will claim that their rights are being infringed upon if some sites are blocked or filtered. “What would the criteria be? What line is it that doesn’t get crossed in terms of what gets blocked or accessed? It can put the airlines in a tough position.”

If you’re seated next to someone viewing content you object to, here are few things to keep in mind:

Don’t look. That’s impossible sometimes, I know. But you could try to focus on your own laptop or book, or close your eyes and take a nap.

Say something. As calmly and politely as possible, let the person know that you’d appreciate it if they turned the offensive material off, or at least turned the screen away from your line of sight.

Ask for assistance. American Airlines flight attendant Frank Bastien says crew members “want to keep everyone happy,” so they may ask a passenger to watch something else, turn their screen or wait until they’re off the plane to view the material. Or they might move you to a different seat — but don’t count on that. Bastien warns that “with planes flying so full these days, finding an empty seat can be impossible.”

Parents, meanwhile, should install filtering software on any laptop or Web device a child will use on an airplane. Airlines may some day put parent control options on in-flight Internet service, but why wait?

If you’re someone who wants to watch something on your laptop that a seatmate should not see or might not appreciate seeing (i.e. anything from a confidential memo to pornographic material):

Get — and use — a privacy screen. No excuses. The screens are inexpensive, lightweight and sold in many airport electronics shops. Airlines rolling out in-flight Wi-Fi may even begin selling privacy screens on planes.

Don't do it. If you forgot your privacy screen but still want to surf pornographic sites, play violent video games or screen childbirth videos, fight the urge. Airplanes are cramped, commercial spaces and you have a responsibility not to offend those seated around you.

“As my grandmother used to tell me,” Harteveldt says, “just because you can do it doesn’t mean you should do it.”

Harriet Baskas writes msnbc.com's popular weekly column, The Well-Mannered Traveler. She is the author of the “Stuck at the Airport” blog, a contributor to National Public Radio and a columnist for USATODAY.com.